According to the materials I possess or can find on the Internet, Georgian adverbs derived from nouns end in -ად (-ad) (unless the noun in the nominative ends in -ო (-o) or -უ (-u), in which case the adverb will end in -ოდ (-od) or -უდ (-ud), respectively.
This is in fact the adverbial case of the noun. Adjectives also have an adverbial case which is just the bare stem without an ending.
However I've just come across the word მწარედ (mtsared) "bitterly" which is related to the word მწარე (mtsare) "bitter". As you can see it ends in -ედ (-ed).
Is this just an irregular inflection peculiar to this word, or is there a regular adjective → adverb process that I just haven't been able to find?